The present invention relates to a vehicle dynamic control system for improving the handling stability of the vehicle and reducing the size and weight of the system, and more particularly, to a rear wheel toe angle control system in which both rear wheels with toe angles are operated by a single reduction gear, whereby the change in the toe angles of both the rear wheels are synchronized.
In general, a suspension is installed on a vehicle between the body and the wheel and connects the two rigid bodies to each other using one or more links. The suspension includes a trailing arm, a knuckle, a control arm and the like.
The suspension effectively absorbs irregularities on a road surface encountered during driving, thereby providing ride comfort. Also, the suspension appropriately controls the roll of the vehicle body caused by the driver's steering or unevenness of the road surface, thereby giving better control to the driver. In addition, the suspension keeps the tire in contact with the road at a suitable level when the vehicle runs on an irregular road, thereby ensuring handling stability of the vehicle when the vehicle turns or brakes.
Meanwhile, when a vehicle turns, it may oversteer or understeer due to vehicle velocity or lack of friction with the road surface, thereby deteriorating the handling stability of the vehicle. In order to solve this problem, the Korean Patent No. 511742 (Aug. 25, 2005) issued to the present applicant discloses a rear wheel toe angle control system (AGCS: Active Geometry Controlled System) for improving dynamic control and handling stability of a vehicle by controlling the length of a rear control arm and therefore the rear wheel toe angles when a vehicle turns.
FIG. 1 is a view showing a rear wheel toe angle control system of a vehicle according to a prior art. Referring to FIG. 1, a rear wheel toe angle control system 20 includes a pair of actuators 22, 23 respectively installed to the left and right ends of a rear cross member 12. It also includes links 26, 27 for connecting the actuators 22, 23 to the left and right rear wheels 14, 15 and changing the toe angles of the left and right rear wheels 14, 15 by means of rods 24, 25 installed to the actuators 22, 23.
The actuators 22, 23 are hydraulic actuators. As the rods 24, 25 of the actuators 22, 23 are translated, the links 26, 27 control the toe angles of the left and right rear wheels 14, 15.
The conventional rear wheel toe angle control system 20 of a vehicle so configured operates the actuators 22, 23 when the vehicle turns to prevent the vehicle from oversteering or understeering. Meanwhile, the applicant has recently developed a vehicle rear wheel toe angle control system to rapidly control the toe angles of the rear wheels 14, by using an electric-powered actuator in order to improve the slow response of a hydraulic actuator.
In the electric-powered actuator, an upper portion of the housing is mounted with a hall type limit sensor, which includes a hall element and a permanent magnet to stably control the position of the rod. A guide made of non-magnetic material is installed around the permanent magnet to improve the sensing ability of the hall element by concentrating the magnetic flux of the permanent magnet. The electric-powered actuator is configured so that the sliding guide is coupled to the inner surface of the housing to guide the linear movement of the rod.
The aforementioned rear wheel toe angle control system of a vehicle, in which the actuators are mounted on the left and right portions of a rear wheel cross member, controls the toe angle of the outer wheel of a turning vehicle in order to prevent an oversteering or understeering phenomenon by increasing or decreasing the friction force between the tire and a road surface.
However, the conventional rear wheel toe angle control system 20 of a vehicle is provided with the two actuators 22, 23 for controlling the left and right rear wheels 14 and 15. Accordingly, there is a limit in installing the actuators 22, 23 due to a narrow installation space, and the two actuators 22, 23 increase weight and manufacturing costs of a vehicle. In addition, with the two actuators 22, 23 used in the prior art, the toe angles of the left and right rear wheels 14, 15 are controlled independently, which may result in unstable control of the vehicle.